GB2616026A

GB2616026A - Filter material

Info

Publication number: GB2616026A
Application number: GB2202520.9A
Authority: GB
Inventors: Fidler Jon; Crouch Michael
Original assignee: Modla Ppe Ltd
Current assignee: Modla Ppe Ltd
Priority date: 2022-02-24
Filing date: 2022-02-24
Publication date: 2023-08-30
Also published as: GB202202520D0

Abstract

The filtering material comprises an air permeable membrane comprising electro-spun nanofibres (12a, 12b, 12c) deposited on a polypropylene (PP) substrate (14a, 14b). The preferred filter comprises 1-3 membranes sandwiched between outer PP layers (14a, 14b), which provide liquid protection. The filter is produced by electrospinning nano-fibres onto spun-bonded, non-woven PP sheet, laser cutting or ultrasonically welding the sheet to produce filters of specified thickness, weight, width and hight. Also claimed is a face mask including the filter.

Description

FILTER MATERIAL

FIELD

Aspects and embodiments of the present invention relate to filter material for use in connection with face masks and respirators.

BACKGROUND

High performance filters for industrial / healthcare respirators have traditionally (for at least the last 60 years), comprised a filtering piece, and a cartridge style casing to 1) hold the filter in place and 2) make it easier to handle. Several problems with this include: that it is large and cumbersome, expensive to manufacture, very difficult to recycle (due to inadequate recycling ecosystems and composite plastics). The cartridge, is a plastic (usually ABS or PVA). The filtering material is also typically at primarily made of plastics such as polypropylene. The polypropylene filtering material is usually configured using a combination of meltblown and/or spunbound techniques.

Meltblown polypropylene comes out of a nozzle like candyfloss and creates an electrostatic charge that is very effective at filtering. Spunbound polypropylene creates a more rigid structure, and is used in products such as diapers and wet wipes that all contain significant volumes of plastic. There are many different process and material variations in connection with meltblown and spunbound polypropylene. The broader industry for these processes and materials is called "non-wovens".

Many Personal Protective Equipment Products (PPE) utilise non-woven materials and utilise the codes "S" to denote that a layer of material protects against liquids and "M" to denote that a layer of material protects against aerosols. Therefore, a filter material that comprises external layers intended to protect against liquids with a sandwich layer intended to protect against aerosols would be referred to as "S/M/S".

S/M/S filters are recognised as having excellent filtration properties, but this comes at the expense of a large surface area that is necessary to lower air resistance and enable the wearer of a mask to breathe. There are generally two options available to manufacturers: i) provide a filter material with disproportionately large dimensions, i.e., in the form of a disposable face mask; or ii) provide a cartridge within which the filter material is pleated to allow the surface area of the filter material to be increased within a manageable space envelope. In the latter case several cartridges may be used to help lower the air resistance further in order to make it easier for the wearer of a mask to breathe. In each case, the mask itself or cartridge is designed to be disposable thus contributing to significant volumes to landfill or incineration (both of which are problematic as they release Persistent Organic Pollutants (POP'S) into the atmosphere). This problem is now particularly acute with the volume of respirators, face masks and filter material used in to protect front line responders against the risk of catching COVID-19, and other respiratory diseases.

It is against these problems that the present invention has arisen.

SUMMARY

One aspect of the present invention provides a filter material comprising an air permeable membrane material formed from an electrospun nanofibre deposited on a polypropylene substrate.

Use of electrospinning to provide a nanofibre based filtration material results in a lightweight, complex scaffold structure that provides 1) higher particulate filtration and 2) lower air resistance and thus, enhanced breathability when compared to a conventional meltblown or spunbound filter material of equivalent surface area. Furthermore, the electrospinning manufacturing process does not impart an electrical charge to the filter material. This means that the shelf life of the filter material is drastically improved. As a consequence, use of an electrospun filter material can reduce the amount of material required for use in a face mask or respirator and wastage from old stocks. The use of separate cartridge components using pleated material may also be eliminated.

In one embodiment, the filter material further comprises a pair of outer layers primarily formed from polypropylene within which the air permeable membrane is sandwiched.

Used as part of a sandwich construction, i.e., with the membrane material forming the filling, excellent filtration results can be achieved. The outer layers of polypropylene provide protection against ingress of liquids, whereas the membrane material provides protection against ingress of aerosols.

The air permeable membrane may comprise exactly one layer of membrane material.

Testing has determined that use of one layer of membrane material according to embodiments of the invention results in filtration of around 80% of aerosol particles smaller than 2 micrometres in the form of mechanically generated particles, chrysotile, and silica dust. This is sufficient to achieve FM P1 classification in the United Kingdom and European Union.

The air permeable membrane may comprise two layers of membrane material.

Testing has determined that use of two layers of membrane material according to embodiments of the invention results in filtration of at least 99% of aerosol particles between 0.1 micrometres and 1 micrometre in the form of mechanically and thermally generated particles, chrysotile, silica dust, solid and liquid particles that do not contain oil, non-toxic household cleaners and disinfectants and non-toxic dusts from sanding, grinding, sawing and insulating particles. This is sufficient to achieve an FM P2 classification under EN 1827 in the United Kingdom and European Union.

The air permeable membrane may comprise three layers of membrane material.

Testing indicates that use of three layers of membrane material according to embodiments of the invention results in filtration of over 99.92% of aerosol particles between 0.1 micrometres and 1 micrometre in the form of mechanically and thermally generated particles, chrysotile, silica dust, solid and liquid particles including those containing oil, non-toxic household cleaners and disinfectants, non-toxic dusts, mists and fumes from sanding, grinding, sawing and insulating particles, mist droplets from spraying and organic vapours and gases. This is extremely close to achieving an FM P3 classification under EN 1827 in the United Kingdom and European Union.

The filter material may be provided on a roll or sheet.

The filter material may be laser cut or ultrasonically welded to a size suitable for use in a face mask for the purpose of air filtration.

The filter material when laser cut or ultrasonically welded may have a width of approximately 157mm and a height of approximately 97mm.

The filter material may have a thickness of approximately 0.7mm.

The filter material when laser cut or ultrasonically welded in accordance with above dimensions may have a weight of approximately 0.76g when the at least one layer of electrospun material is exactly two layers.

The pair of spunbound polypropylene layers may provide protection against liquid ingress.

Another aspect of the invention provides an air filtering mask comprising: a housing or attachment means for receiving a soft body; a soft body formed from multiple layers of material including at least one layer of air filtering material; and a pair of layers of material having liquid protection properties positioned either side of the at least one layer of air filtering material.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. The detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended to be given by way of example only.

FIGURES

Aspects and embodiments of the invention will now be described by way of reference to the following figures.

FIG. 1A illustrates a layered construction of a first embodiment of filter material according to an aspect of the invention.

FIG. 1B illustrates a layered construction of a second embodiment of a filter material according to an aspect of the invention.

FIG. 1C illustrates a layered construction of a third embodiment of a filter material according to an aspect of the invention.

FIG. 2 is a plan view of a filter for a face mask according to embodiments of the invention.

DESCRIPTION

The following description of the preferred embodiment(s) is merely exemplary in nature and is no way intended to limit the invention, its application, or uses.

The description of illustrative embodiments according to principles of the present invention is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description of embodiments of the invention disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present invention. Relative terms such as "lower," "upper," "horizontal," "vertical," "above," "below," "up," "down," "top" and "bottom" as well as derivatives thereof (e.g., "horizontally," "downwardly," "upwardly," etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in a particular orientation unless explicitly indicated as such. Terms such as "attached," "affixed," "connected," "coupled," "interconnected," and similar refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. Moreover, the features and benefits of the invention are illustrated by reference to the exemplified embodiments. Accordingly, the invention expressly should not be limited to such exemplary embodiments illustrating some possible non-limiting combination of features that may exist alone or in other combinations of features; the scope of the invention being defined by the claims appended hereto.

As shown in FIGs 1A-1C, embodiments of an aspect of the invention define a filter material (10) comprising at least one layer of an electrospun nanofibre based material (12a, 12b, 12c) sandwiched between outer layers of a polypropylene material (14a, 14b). The polypropylene material (14a, 14b) may be spunbound and provides protection against liquids. The electrospun nanofibre material (12a, 12b, 12c) provides filtration protection against aerosols. Depending on the required filter performance, the electrospun nanofibre based material (12a, 12b, 12c) may comprise one, two, three, or more, layers. In the present disclosure, up to three layers of electrospun nanofibre based material (12a, 12b, 12c) are envisaged. Of course, some applications may utilise greater than four layers of electrospun nanofibre based material (12a, 12b, 12c). In some embodiments, the electrospun nanofibre based material (12a, 12b, 12c) may be an electrospun polypropylene based material.

The applicant has observed that use of a single layer of electrospun nanofibre based material (12a) sandwiched between outer layers of a spunbound polypropylene based material enables the filtration of at least 80% of particles between 0.1 and 1.0 micrometres. Such a construction has been determined to be suitable for filtering mechanically generated particles, chrysotile and silica dust.

When two layers of electrospun nanofibre based material (12a, 12b) are sandwiched between outer layers of a spunbound polypropylene based material, at least 94% of particles between 0.1 and 1.0 micrometres are filtered out. Such a construction has been determined to be suitable for filtering mechanically and thermally generated particles, chrysotile, silica dust, solid and liquid particles that do not contain oil, nontoxic household cleaners and disinfectants and non-toxic dusts from sanding, grinding, sawing and insulating particles.

When three layers of electrospun nanofibre based material (12a, 12b, 12c) are sandwiched between outer layers of a spunbound polypropylene based material, at least 94% of particles between 0.1 and 1.0 micrometres are filtered out. Such a construction has been determined to be suitable for filtering out mechanically and thermally generated particles, chrysotile, silica dust, solid and liquid particles including those containing oil, non-toxic household cleaners and disinfectants, non-toxic dusts, mists and fumes from sanding, grinding, sawing and insulating particles, mist droplets from spraying and organic vapours and gases.

It will be appreciated that the use of a greater number of layers of electrospun nanofibre based materials (12a, 12b, 12c) may be used to provide an ever-increasing percentage filtration of particles between 0.1 and 1.0 micrometres. However, the skilled person would need to bear in mind the increased air resistance caused by increasing the thickness of the filter material (10). The greater the air resistance, the more difficult it is to breathe through the filter material (10). Furthermore, simply increasing the number of layers of electrospun nanofibre based materials (12a, 12b, 12c) would provide diminishing returns.

The electrospun nanofibre based material (12a, 12b, 12c) may be provided on a sheet or roll. To manufacture the filter material, the desired numbers of electrospun nanofibre material (12a, 12b, 12c) and the outer layers of spunbound polypropylene material (14a, 14b) are overlaid on top of each other. The layer construction is then laser cut or ultrasonically welded at an appropriate temperature to form the desired shape of filter and to seal the edges of the cut shape thus preventing fraying.

As shown in FIG. 2, the filter material (10) may be laser cut or ultrasonically welded into a shape suitable for use in connection with a face mask body and/or respirator. The resulting filter (100) may have a maximum width of 157.52mm and a maximum height of 96.73mm. It will be appreciated that such dimensions are given by way of example and are not intended to be limiting. Other applications, including other types of face masks and/or respirators, may require a filter of differing dimensions. The thickness of the filter (100) depends on the number of electrospun nanofibre based material layers (12a, 12b, 12c). In the case of two layers, the thickness of the filter (100) is 0.7mm. Similarly, the weight of the filter (100) depends on the number of electrospun polypropylene material layers (12a, 12b, 12c). Each layer of spunbound is 0.3g and each SMS layer is 0.4g. In the case of two layers, the weight is 0.76g. In

S

the case of three layers, the weight is 1.4g. It will be appreciated that all dimensions and weights are given by way of example only and should be construed as limiting the claims in any way.

The above embodiments are exemplary only, and other possibilities and alternatives within the scope of the appended claims will be apparent to those skilled in the art.

Claims

CLAIMS1. A filter material comprising an air permeable membrane material formed from an electrospun nanofibre deposited on a polypropylene substrate.
2 A filter material according to claim 1 further comprising a pair of outer layers primarily formed from polypropylene within which the air permeable membrane is sandwiched.
3. A filter material according to claim 1 wherein the air permeable membrane material comprises exactly one material layer.
4. A filter material according to claim 1, wherein the air permeable membrane material comprises exactly two material layers.
5. A filter material according to claim 1, wherein the air permeable membrane material comprises exactly three material layers.
6. A filter material according to any preceding claim, wherein the filter material is provided on a roll or sheet.
7. A filter material according to any preceding claim laser cut or ultrasonically welded to a size suitable for use in a face mask for the purpose of air filtration.
8. A filter material according to claim 6, wherein the laser cut, or ultrasonically welded filter material has a width of approximately 157mm and a height of approximately 97mm.
9. A filter material according to claim 6 or claim 7 having a thickness of approximately 0.7mm.
10.A filter material according to any of claims 6 to 8, wherein the laser cut or ultrasonically welded filter material has a weight of approximately 0.76g when the air permeable membrane material is exactly two material layers.
11.A filter material according to any preceding claim wherein the pair of polypropylene layers provide liquid protection.
12.An air filtering mask comprising: A housing or attachment means for receiving a soft body; a soft body formed from multiple layers of material including at least one layer of air filtering material and a pair of layers of material having liquid protection properties positioned either side of the at least one layer of air filtering material.
13.An air filtering mask according to claim 12, wherein the at least one layer of air filtering material is exactly one layer.
14.An air filtering mask according to claim 13, wherein the at least one layer of air filtering material is exactly two layers.
15.An air filtering mask according to claim 14, wherein the at least one layer of air filtering material is exactly three layers.
16. An air filtering mask according to any of claims 12 to 15 further comprising means for attaching the soft body to a face of the wearer.